1. Technical Field
This invention relates generally to radio controlled (RC) models, and more particularly to a fuse-protected controller for an RC model car.
2. Background Information
A typical RC model car race may have ten or more operators simultaneously racing 1/10 scale RC model cars around a carefully groomed 450 foot track at lap speeds in the 16-second range. But even with a model car fully outfitted and finely tuned, the winner may only edge out the runnerups by a few seconds or less. That, of course, encourages attention to details of RC model car construction and operation in preparation for the next race, and so such competitive activity makes each of those details important.
One detail concerns overall efficiency, especially efficient use of battery power, and RC racing enthusiasts go to great lengths to achieve a one or two percent improvement by such things as fine tuning gear ratios, testing and selecting battery cells, changing armature windings, and so forth. They may even omit fuse protection to avoid fuse bulk and weight and a small voltage drop across the fuse. But doing so can cause problems. When the operator hastily installs the battery just before the race, for example, he may inadvertently reverse polarity and thereby damage the controller beyond use.
To better visualize the problem, consider a typical RC model car. It includes a DC motor for driving the wheels, a nicad battery for supplying power to the motor, and a controller for regulating the flow of power from the battery to the motor according to commands received by radio from the operator. The controller usually includes a complement of electronic components on a small printed circuitboard to which the battery and motor are connected by suitable wiring, and some previous attempts at fusing the RC car employed a fuse in the wiring between the battery and controller. But such an arrangement introduces the undesired bulk, weight, and small voltage drop previously mentioned. So some operators choose to do without a fuse, thereby leaving the controller vulnerable to damage.
Although conceivable to place a fuse on the controller circuitboard in the main power line coupling the controller circuitry to the battery, some existing fuses for printed circuitboards must be soldered in place on the circuitboard. That makes replacement quite inconvenient. Others plug into spring clips on the circuitboard that mechanically grip the fuse while providing electrical contact. But such spring clips can be somewhat bulky as well as being prone to fatigue and eventually fail. Furthermore, existing fuses that are small enough to place on a controller circuitboard may have a current rating that is insufficient for the amount of current needed to power the motor, which may be as much as fifty amperes. Moreover, fusing the main power line still introduces a small, undesired voltage drop. So, racing enthusiasts and other RC operators need a better way to overcome the problem.